Annals of Arid Zone-23(l),
55-62, 1984
Suspended material and solute concentration in flash flood water
of Luni rher and its tributaries
J. S.
Central
CHOUDHARI,
K. D.
SHARMA
NND
Arid Zone Research Institute,
N. S.
VANGANI
Jodhpur-342
003
ABSTRACT
Suspended material and chemical composition of the flood water of the Luni
river and its tributaries draining an area of about 34, 866 km2 in arid part of western
Rajasthan reveals that, suspended sediments were two to three times higher during
flood (5830-13920 Cumec) than during low flows (495 to 1192 Cumec). Solute
concentration show reverse trend because of dilution, to that of suspended
sediment. Lithology of the area controls the sodium, potassium, calcium and
mangnesium concentrations during flows.
INTRODUCTION
Occurrence of floods in desert streams
especially in the Luni in Western Rajasthan
is a rare event.
Such an instance had
occurred during July 1979 after a period
of 117 years (Sharma et af., 1980) in the
living memory.
Along with a colossal
amount of water, a mass of suspended
and dissolved materials were transported
rlownstream
and
thereby
influenced
physical and biological
conditions
in
receiving systems.
However, so far no
data are available on transport characteristics of Luni and its tributaries during
normal and flood flows. Therefore,
the
authors have tried in this paper to work
out the water chemistry of high and low
flows in the Luni and its tributaries
during 1979 which will help in planning
the water resource management in Indian
desert.
THE
LUNI
BASIN
The Luni with its tributaries
viz.,
. Jojari, Guhiya, Bandi, Sukri, Mitri, Jawai,
Khari, Khari Bandi and Sagi forms the
only integrated
drainage system in the
arid Western Rajasthan.
It rises in the
Aravalli hill ranges near Ajmer (260 27'
N, 74° 39' E) and after an initial SWjW
course towards Barmer flows SW until it
drains into the NE corner of the Rann of
Kutch (Fig. 1). This river system occasionally carry water generated in direct
response to torrential
rainfall
during
monsoon period and remains dry for rest
of the year. The approximate basin area
of the Luni is 34, 866 km2 (CAZRI,
1963) .
The entire Luni basin is situated on
hard rock and massive rock formations
composed of volcanics, crystallines and
56 :
et al.
J. S. CHOUDHARI
metamorphics,
whereas the western part
is covered with deep alluvium.
All these
formations occur at very shallow depths
below alluvium and/or below sand cover
varying from less than I m to over 40 m.
Occurrence of CaCOa pan is a common
characteristics
of the terrain
and
is
encountered at depths varying from 13 to
I 12 em in river courses and 48 to 152 em
in plains (CAZRI, 1963).
MATERIAL
AND
METHODS
Water samples were collected from 23
gauging stations (Fig. I) whenever the
flow exceeded
45 em depth.
These
samples were transported
to laboratory
and filtered.
Suspended
material
on filter
paper dried, weighted and expressed in
g/l.
The filtrates
were analysed
for
pH,
conductivity,
total
sodium, potassium,
sium, and are reported
RESULTS
AND
dissolved
calcium
and
solids,
magne-
in ppm.
DISCUSSION
The precipitation,
flow characteristics
and causes of the flash flood occurred in
Luni basin during 1979 are reported by
Sharma and Vangani (1982) and Sharma
et al. (1982). The data on total suspended
solids (TSS) in the Luni and its tributaries (Table I and Fig. 2) revealed that
during the high flow (5830-13920 Cumec)
period it was about 2 to 3 times than
during tbe low flow (495- II 92 Cumec).
Such high load concentrations
are due
to vulnerability
of sparsely
vegetated
sandy and rocky slopes to erosion by
heavy rainfall and flash runoff.
The
suspended
load
concentrations
during
flood (high flow) attained between 860 to
40,200 ppm which is quite in agreement
with the 12,000 ppm in the water of Todd
river at Alice springs in the Central
Australian floods of 1967 and concentrations greater than 5,000 ppm are typical
of floods throughout the arid western U.S.
(Mabbutt, 1977). It increased sharply at
downstream
to Samdari
and Gandav
partly due to addition
from different
tributaries and mainly due to excavation
and diminishing of flood discharge.
The
waters
from
all the streams are
alkaline in nature and total dissolved
solids (TDS) increased down-stream
as
the tributaries
join the Luni (Fig. 3,
Table 1). The solute concentration
in
various
stream
originating
from the
different lithology and geology revealed
that spatial patterns of the TDS during
the flood flows was much less than the
low flows. This reduction during flooding
was due to dilution.
Similar distribution
patterns
have been reported
for the
Salt river, Kentucky
(Hendrickson
and
Krieger,
1964),
Salt river,
Arizona
(Rinne,
1975) and Sycamore
Creek,
Arizona (Fisher and Minckley,
1978).
Further
river Guhiya
had contributed
higher solutes than the other streams
draining
the various catchments.
The
presence of higher solutes in Bandi after
PaJi was
perhap
due
to
effluent
discharges from tbe dyeing industries
is recorded at Jaitpur.
and
The concentrations
of some selected
cations revealed that by far all the waters
57
SOLUTES IN FLASH FLOOD WATERS
~o
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or •••
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r,
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58
: J. S. CHOUDHARI
at.
et
Table 1. Suspended and solute concentration
Streams
catchment
Station
in high and low flows in Luni basin during 1979
TDS* (g/l)
TSS** (gjl)
High
flow
Luw
flow
High
flow
Low
flow
Mitri/Jojri
Bisalpur
0.133
0.227
1.28
1.65
Luni
Jasnagar
0.166
N.F.
0.86
N.F.
Banjakuri
0.159
N.F.
4.65
N.F.
Bilara
0.126
0.224
2.48
3.52
Samdari
0.544
0.860
14.88
1.98
Gandav
0.640
1.760
40.20
7.57
5.90
N.F.
Sojat
0.063
N.F.
Sheopura
0.066
N.F.
5.15
N.F.
Singari
0.307
0.518
2.63
0.91
Soneimaji
0.307
N.F.
10.00
N.F.
Pali
0.570
N.F.
11.40
N.F.
Jetpur
0.218
1.529
11.31
7.57
Khari Bandi
Madgaon
0.563
0.448
2.03
4.30
Sagi
Sewari
0.256
N.F.
6.62
N.F.
Guhiya
Bandi
Note - N. F.
=
No flow
* TDS
**
=
Total dissolved solids.
TSS = Total suspended solids.
are sodium dominated
except the waters
from Jojri, Sagi and upper Luni catchments which have calcium as dominant
cation (Figs. 4 and 5). Under high flow
conditions about three fourth of the basin
area drained waters containing 25 ppm
sodium, whereas the waters from the same
area under low flow conditions
contain
100 - 300 ppm
sodium.
Similarly,
the
lower part of the basin which under the
high flow conditions drained 50 ppm Na
drained 300-500 ppm Na during the low
flow conditions.
Similar concentration
patterns were observed for potassium ion
also. Calcium (Fig. 5) being the next
dominating
cation, three fourth of the
basin area drained 10-30 ppm Ca under
high flow conditions drained 20-80 ppm
l
SOLUTES IN FLASH FLOOD WATERS
rOTAL
TOTAL
SUSPENDED SOLIDS IN HIGH AND
DISSOLVED
SOLIDS
59
IN HIGH AND
LOW FLOWS OF LUNI BASIN DURING· 1979
LO~ FLOWS OF LUNI BASIN DURING 1979
t~
I
I
I
.
14
~-I
HIGH FLOW
lOlAOf'
LOW FLOW
SC.••..••
Fig. 2.
lolU
HIGH FLOW
Cl.A IY
CRQ,(lc"a~I"'L.oII
.••
~"""O<..,._".••
c ••• ·...,_
Total suspended solids in Luni
basin during 1979.
. under the low flow conditions.
Magnesium content has shown a different pattern
than the above three cations (Fig. 5).
Half of the: basin!draining
eastern part
fjhave 3-6 ppm Mg under high flow conditions, drained 3-9 ppm under the low
flows. The remaining half, lower part
which was draining 6 ppm Mg under high
f1ow:conditions drained 15-21 ppm during
the low flows.
In terms of the above dissolved sub~tances, floods are often viewed as dilution
CIACLE.!C.,.l:-:
SC~E
e
LOW FLOw
..fTO'S,i'a/Lrt!
.,/L.t
.t.·
•••,'-o..OC'l_'Qh
t
.O~••h.
Fig. 3. Total dissolved solids in Luni basin
during 1979.
phenomena
in which low conductivity
rain water dilutes ground water that are
nearer chemical equilibrium
with substrata and thus rich in dissolved saIts.
Therefore low concentrations
under high
flow conditions
are
observed.
This
dilution
effect is partially
offset by
leaching and dissolution
of sol utes from
newly exposed rock and soil minerals as
well as from the suspended particles and
thus higher concentrations
are observed
under subsequent
low flows. Similar
_
60
1. S. CHOUDHAR
I
et af.
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ell
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SOLUTES IN FLASH FLOOD WAT ERS
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61
62 :
J. S. CHOUDHARJ
et al.
results were also reported by Johnson and
Needham (1966), Hem (1967) and Fisher
and Minck1ey (1978).
The variation in total dissolved substances and cations amongst the various
catchments is mainly due to the lithology
of the area.
Eastern part of the basin
which is dominated by schist, gneiss and
calc-schist and slow weathering
environment yielded, less salts than the lower
half of the basin, which is covered by
alluvium, have salts on the surf.lces due to
high temperature are added to the runoff
in the rainy season.
Rodda et al (1976)
reported lithological
control on solute
concentrations
to greater extent than the
other factors.
ACKNOWLEDGEMENTS
We are grateful to Dr H. S. Mann
and Dr. K. A. Shankarnarayan,
Director
and Head of Division, respectely, CAZRI,
Jodhpur, for facilities and encouragement
during the study.
REFERENCES
Hem, J. D. 1967. Study and interpretation
of the chemical characteristics
of
natural
waters.
U. S. Geological
survey, water supply paper 1473: 1363.
Hendrickson, G. E. and Krieger, R. A.
1964. Geochemistry of the natural
waters of the Blue grass region,
Kentucky.
U S. Geological survey,
lVater supply paper 1700: 1-135.
Johnson, C. M. and Needham, P. R. 1966.
Ionic composition of Sagehen creek,
California,
following an adjacent
fire. Ecology 47: 636-639.
Mabbutt,
J. A. 1977. Desert Ilandforms.
Australian National University Press,
Canberra.
Rinne, J. N. 1975. Hydrology of the Salt
river and its reservoirs,
central
Arizona.
Arizona
Academy
of
Sciences 10: 75-86.
Rodda, J. c., Dowing, R. A. and Law,
F. M. 1976. Systematic Hydrology.
Newnes-Butterworth,
London.
Sharma, K. D. and Vangani, N. S. 1982.
Some rainfall festures of July 1979
storm
over
Luni Basin
Ann. Arid
Zone 21 (I): 22-32.
CAZRI I1J63. Basic resources of Central
Luni basin,
Western
Rajasthan.
Divisonal report No. 63/1.
Fisher,
S. G. and Minckley, W. L. 1978.
Chemical characteristics
of a desert
stream
in flash flood. J. Arid
Environ. 1: 25-33.
Sharma, K. D., Vangani, N. S., Chatterji,
P. C. and Ganga
Singh
1982.
U nprecendented
floods
in Lun i
basin, Western Rajasthan
during
July 1979-A case study.
Mal/sam
33(3): 377-384.